| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 97 === Seventy two bacterial isolates were examined the ability of production Indole-3-acetic acid (IAA). Among them, Gh1 and Gh4 isolates produced the highest concentration of IAA (61~80 mg/L), followed by Bg12 and Bg31 isolates. These isolates (Gh1, Gh4, Bg12 and Bg31) were identified as Paenibacillus polymyxa, Geobacillus thermoblucosidasius, Bacillus megaterium and Microbacterium resistense ,respectively. The L-form tryptophan was a determinant factor for these isolates to produce IAA. The production of IAA was increased, with the increase of tryptophan in LB (Luria-Bertani) broth. The ability of producing IAA by bacterial isolates grown in different commercial media was tested. The tryptic soy broth (TSB) showed the best effect for these isolates to produce IAA, and increased the biomass of bacterial isolates. The seeds of tomato, melon and radish were dipped into bacterial cell suspension and sown in peat moss. The results indicated that Bg31, Gh1 and Gh4 isolates could significantly promote the seedlings growth of melon and tomato. The Bg31 isolate showed marked effect on promoting the growth of radish seedlings when its culture filtrate of TSB was added into peat moss before sowing. In addition, the Bg31 isolate cultured in TSB showed similar effect on promoting branch root development of radish seedlings as treatment with IAA standard. For practical use, a formula consisted of molasses and peanut seed pomace meal was used for culturing Bg31 isolate and showed significant effect on promoting the growth of radish plants.
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